Roe was a landmark decision for its supporters. They say that abortion is now safer and occurs earlier in pregnancy than ever before. But some supporters of a woman's right to choose have criticized the decision, arguing in part that the court ruled more broadly than it needed to.

When Roe v. Wade came down, abortion was illegal in 30 states, but some states were pushing toward liberalizing abortion laws. Roe called into question the criminal abortion statutes of every state, even those with less restrictive provisions.

Justice Ruth Bader Ginsburg, before she was nominated to the Supreme Court, wrote an essay in 1984 for the University of North Carolina School of Law arguing in part that Roe would have been "more acceptable as a judicial decision" if the court had focused on the extreme Texas statue that was before it instead of issuing such a sweeping decision.

"The political process was moving in the early 1970s," Ginsburg wrote, "not swiftly enough for advocates for quick, complete change, but majoritarian institutions were listening and acting. Heavy-handed judicial intervention was difficult to justify and appears to have provoked, not resolved, conflict."

In his book, "From the Closet to the Altar: Courts, Backlash, and the Struggle for Same-Sex Marriage," historian and legal expert Michael Klarman talks about the backlash Roe created.

"When the court intervenes to defend a minority position or even to resolve an issue that divides the country down the middle, its decisions can generate political backlash, especially when the losers are intensely committed, politically organized and geographically concentrated."

Major gay-rights organizations plotted their own gay-marriage strategy years ago, hoping to move first at the state level to advance their cause to avoid a damaging federal court decision that might slow momentum or slam shut courthouse doors.

"It's no secret that increased political support for marriage equality at the local, state and national levels is obviously very helpful toward our ultimate goal of winning marriage equality across the country, whether it's through the Supreme Court or otherwise," Janson Wu, a staff attorney at Gay & Lesbian Advocates & Defenders, said.

Nine states and the District of Columbia allow gay marriage, and gay-rights advocates believe several other states will soon follow suit.

With that momentum behind them, they will head to the Supreme Court in March for a case regarding California's ban on same-sex marriage. The case asks a very broad question: Do same-sex couples have a fundamental right to marry under the U.S. Constitution? But there are a number of ways the court could rule in favor of gay rights, without reaching that big question.

Gay advocates want a win. But some would be satisfied with a narrow victory that would continue the momentum and allow them to work on the state level to get more states on board, before perhaps returning to the Supreme Court.

One such ruling would focus on the "lack of justification for giving same-sex couples all the rights and responsibilities of marriage but withholding the word 'marriage' from them." The ruling would affect only a few other states, including California.

Without even the tea leaves of oral arguments, it's far too early to guess how the court might rule.

But gay-rights advocates hope that if the Supreme Court issues a broad opinion in their case, the 40th anniversary of the ruling will not include large protests in the streets.